The research proposed is an intensive quantitative study of a small (30-celled) integrative system, the stomatogastic ganglion of the spiny lobster. A group of fourteen cells comprising the "pyloric cycle group" will be selected for detailed study of: 1) Activity patterns produced and their reaction to perturbations; 2) Repetitive firing properties (pacemaker sensitivity, adaptation, rebound, reaction to perturbations as a function of phase in firing cycle) of each individual neuron type; 3) Synaptic interactions (PSP shape, physiological effectiveness, reversal potential and facilitation effects, electrotonic and "chemotonic" (D.C. chemical) interactions) for all interacting pairs; and properties and mechanisms of burst production in the cells generating the basic pyloric rhythm. 4) The principal goals of this will be production of a series of physiologically reliable computer models of the system. As more quantitative data become available, progressively more accurate models will be produced. The models in turn will be used as a means for confirming or rejecting theories on pattern production in the ganglion; for uncovering additional factors in the ganglion that are contributory to its physiological properties; and for investigating the stability of patterns to parameter variation to gain insight into why physiological properties are set as they are.